Sub-pascal unidirectional flow valves

A valve for use in a microfluidic system, the valve comprising:

• a body including an inner bore extending between a first port and a second port, a seat having an opening and being disposed within the inner bore, and a plurality of restrainers positioned between the seat and the second port;
• and
• a disk that is moveable relative to the seat and the plurality of restrainers such that application of a first predetermined pressure that is between about 0.05 pascals and 1 pascal causes the disk to move from a first position towards a second position to permit fluid communication between the first port and the second port.

A metamaterial scaffold, comprising:

• (i) a structure defining a lumen;
• (ii) at least a portion of an outer or non-lumen surface of the structure is coated with a plurality of biological cells, and wherein the structure is composed of a metamaterial, optionally the structure being a tubular structure defining first and second ends and the lumen.